Coefficiente di frizione a parete

$\displaystyle C_F$	$\displaystyle =$	$\displaystyle \frac{\tau_P}{\frac{1}{2}\rho U^2}$
	$\displaystyle =$	$\displaystyle \frac{\mu \left(\ensuremath{\frac{\partial u}{\partial y}}\right)_P}{\frac{1}{2}\rho U^2}$
	$\displaystyle =$	$\displaystyle \frac{\mu \left(x f^{''}\right)_P}{\frac{1}{2}\rho U^2}$
	$\displaystyle =$	$\displaystyle \left.\mu \frac{x \frac{k \sqrt{k}}{\sqrt{\nu}} F^{''}}{\frac{1}{2}\rho U^2}\right\vert _P$
	$\displaystyle =$	$\displaystyle \frac{2 \sqrt{\nu k} F^{''}(0)}{U}$
	$\displaystyle =$	$\displaystyle 2 F^{''}(0)\sqrt{\frac{\nu k}{U^2}}$
	$\displaystyle =$	$\displaystyle 2 F^{''}(0)\sqrt{\frac{\nu k}{k x U}}$
	$\displaystyle =$	$\displaystyle 2 F^{''}(0)\sqrt{\frac{\nu}{x U}}$
	$\displaystyle =$	$\displaystyle 2 F^{''}(0)\frac{1}{\sqrt{\mathcal{R}e_x}}$